Gearing up for action: attentive tracking dynamically tunes sensory and motor oscillations in the alpha and beta band.

Allocation of attention during goal-directed behavior entails simultaneous processing of relevant and attenuation of irrelevant information. How the brain delegates such processes when confronted with dynamic (biological motion) stimuli and harnesses relevant sensory information for sculpting prospective responses remains unclear. We analyzed neuromagnetic signals that were recorded while participants attentively tracked an actor's pointing movement that ended at the location where subsequently the response-cue indicated the required response. We found the observers' spatial allocation of attention to be dynamically reflected in lateralized parieto-occipital alpha (8-12 Hz) activity and to have a lasting influence on motor preparation. Specifically, beta (16-25 Hz) power modulation reflected observers' tendency to selectively prepare for a spatially compatible response even before knowing the required one. We discuss the observed frequency-specific and temporally evolving neural activity within a framework of integrated visuomotor processing and point towards possible implications about the mechanisms involved in action observation.

Neural mechanisms of movement speed and tau as revealed by magnetoencephalography.

A fundamental aspect of goal-directed behavior concerns the closure of motion-gaps in a timely fashion. In this context, the critical variable is the time-to-closure, called tau (Lee in Perception 5:437-459, 1976), and is defined as the ratio of the current distance-to-goal gap over the current instantaneous speed towards the goal. In this study, we investigated the neural mechanisms of speed and tau in pointing hand movements by recording MEG activity from the whole brain of 20 right-handed healthy human subjects operating a joystick with their right hand. The relations between neural signals and speed and tau were analyzed using an autoregressive multiple regression model, where the time-varying MEG signal was the dependent variable and the corresponding value of speed and tau were the independent variables. With respect to speed, we found that 81% of sensors showed significant relations over the left frontal-parietal, left parieto-temporal, and, less prominently, the right temporo-occipital sensor space. These results document the widespread involvement of brain areas with movement speed, especially in the left hemisphere (i.e., contralateral to the moving limb), in accord with previous studies. With respect to tau, 22% of sensors showed significant relations over the parietal (bilaterally), right parietal-temporal, and, less prominently, the left temporo-occipital sensor space. The tau effects often occurred concurrently with speed effects and spatially overlapped in the left fronto-parietal sensors. These findings document for the first time the time-varying, dynamic processing of information regarding tau in specific brain areas, including the right parietal cortex. This is of special interest, for that area has been found to be involved in processing information concerning the duration of time intervals in perceptual tasks (Harrington et al. in J Neurosci 18:1085-1095, 1998; Rao et al. in Nat Neurosci 4:317-323, 2001). Since tau is itself a time interval, we hypothesize that the right parietal focus of tau processing observed in this study reflects the ongoing processing of tau as an interval for a timely arrival of the hand to the target.

High-frequency neural oscillations and visual processing deficits in schizophrenia.

Visual information is fundamental to how we understand our environment, make predictions, and interact with others. Recent research has underscored the importance of visuo-perceptual dysfunctions for cognitive deficits and pathophysiological processes in schizophrenia. In the current paper, we review evidence for the relevance of high frequency (beta/gamma) oscillations towards visuo-perceptual dysfunctions in schizophrenia. In the first part of the paper, we examine the relationship between beta/gamma band oscillations and visual processing during normal brain functioning. We then summarize EEG/MEG-studies which demonstrate reduced amplitude and synchrony of high-frequency activity during visual stimulation in schizophrenia. In the final part of the paper, we identify neurobiological correlates as well as offer perspectives for future research to stimulate further inquiry into the role of high-frequency oscillations in visual processing impairments in the disorder.